1. Field of the Invention
The present invention relates to an aqueous emulsion, and more particularly, to an aqueous emulsion composition excellent in at least one of solvent resistance, anti-blocking property and heat resistance.
The aqueous emulsion can be used for applications where a surface coated therewith is required to have at least one of the aforementioned properties, that is, solvent resistance, anti-blocking property, and heat resistance. The aqueous emulsion can be used, for example, as undercoating agents for release paper, back surface treating agents, binders for diazo photosensitive paper, and binders for offset masters.
2. Description of the Related Art
Heretofore, as a component for a releasing agent used for a release paper, silicone dissolved in a solvent has been used. Silicone is so expensive that it is necessary to give a sufficient releasing ability with an amount which is as small as possible.
Therefore, in general, silicone is coated on paper after a filling treatment is effected by means of an undercoating layer so as to prevent silicone from infiltrating into the paper.
As such an undercoating layer, there may be mentioned clay coating, coating with an aqueous high polymer such as polyvinyl alcohol, starch and the like, and laminating with polyethylene (U.S. Pat. No. 3,403,045). Recently, coating with a resin emulsion such as acrylic acid ester copolymer emulsions has been proposed (Japanese patent Application Publication No. Sho 63-54035).
Clay coating is heat resistant, but adhesion with silicone is not good, and aqueous high polymers such as polyvinyl alcohol, starch and the like give a fragile coat film and exhibit poor water resistance so that blocking is liable to occur at a high humidity when it is stored with only an undercoating layer. Further when laminated with polyethylene or the like, the product has a high smoothness and is soft, but the heat resistance is poor.
In addition, resin emulsions are excellent in film shapeability, but are poor in heat resistance and solvent resistance, and do not possess a filling effect. A method has been proposed for improving heat resistance and solvent resistance by forming an admixture with oxidized starch (Japanese Patent Application Laid-open No. Sho 60-245683).
For preparing a carrier for a transferable image, paper is treated with a releasing agent and a binder emulsion composed of an acrylonitrile-butadiene rubber is applied to the releasing agent layer (U.S. Pat. No. 3,933,503).